Implant for artificial teeth

ABSTRACT

An implant for artificial teeth, including: an intrabony insert or implant ( 1 ) which is designed to be inserted in a fixed manner in the jawbone and is provided with a cavity ( 10 ); an artificial tooth assembly with a tooth stump ( 3 ) for the respective artificial tooth and a stem to be inserted and fixed in the cavity of the intrabony insert or implant; the cavity ( 10 ) of the intrabony implant has an undercut annular recess ( 12 ) below and above which there are hole portions ( 11,13,14 ) having a smaller diameter, one ( 11 ) of the hole portions, above the recess ( 12 ), being interrupted by at least one longitudinal access slot ( 121 ) for the passage of at least one lug of the stem of the tooth stump ( 3 ) by axial sliding and subsequent rotation, the outer upper end of the intrabony implant being polygonal, the tooth stump ( 3 ) protruding beyond the lug with a polygonal region for the insertion of a polygonal annular bush for the mutual locking of the stump ( 3 ) with respect to the intrabony implant ( 1 ) so as to prevent rotation.

BACKGROUND OF THE INVENTION

The present invention relates to an implant for artificial teeth.

The invention is used particularly but not exclusively in the field ofprosthodontics, where artificial teeth are fitted in the human jaw byinserting a metallic implant for each tooth in the jawbone and by fixinga corresponding artificial tooth therein.

Prostheses for artificial teeth are already known which use:

at least one artificial tooth support, which is designed to replace theroot of the removed tooth and can be stably inserted in the jawbone atthe region where the artificial tooth is to be applied, said supportbeing generally made of titanium and being hollow (this support iscommonly known as intrabony implant);

at least one structure for supporting an interchangeable artificialtooth with a tang for engagement in the recess of the tooth support(commonly known as stump).

The stump and the intrabony implant are coupled by fixing means which,in the current art, are mainly constituted by axial screw means whosedrawback is that they are complicated and expensive as well as difficultto apply.

Furthermore, the screw coupling easily loosens due to the stressesproduced by chewing and this can even lead to breakage of the threads,with possibly severe damage.

A solution to this problem, proposed by the same Applicant, is disclosedin Italian patent application UD 97 A 00084, which provides for animplantation system for artificial teeth of the type which provides fora hollow intrabony insert or implant to be inserted in a fixed manner inthe jawbone and an artificial tooth assembly which has a stumpassociated with means for fixing in said insert.

According to this solution, in the cavity of the intrabony implant thereare at least two annular ridges which are spaced and whose annular shapeis interrupted so that the interruption is formed in one ridge inopposition to the interruption of the other ridge.

The stump also has a protrusion which enters and engages the cavity andhas two lugs at the interruptions in order to pass beyond the ridges byaxial insertion coupling and, by rotation, into corresponding underlyingannular slots, engaging below them so as to prevent extraction.

In this manner, the problems are partially solved; in particular,greater safety against the danger of losing the artificial tooth isachieved.

Even this solution, however, is complicated and particularly expensivedue to the provision of the double annular undercut acting as safetycoupling with rotary insertion coupling, which is necessary in any caseto avoid the danger of disengagement.

Such complexity is further increased by the limited size of theimplants, also in view of the fact that the presence of the doubleundercut reduces the resisting cross-section, with the danger offailure.

Therefore, although the above solution is theoretically valid, it stillentails a structure which is complicated and therefore, despite thehigher safety that it provides, is expensive and therefore applicableonly to users who can afford this higher cost.

Another drawback that occurs in conventional solutions is due to thefact that the annular thickness of the intrabony implant (outsidediameter with respect to the cavity diameter) is necessarily reduced,since the outside diameter is limited by the thickness of the jawbone inthe implantation area, and therefore there is the risk of excessivelyweakening the tang of the stump or the wall of the intrabony implantthat accommodates the tang.

In any case, in view of the extremely intense stresses applied by thejaw during chewing, there is the danger that the former or the lattermay break.

DISCLOSURE OF THE INVENTION

The aim of the present invention is, therefore, to eliminate thedrawbacks noted above in conventional types, providing a new implant forartificial teeth in which the fixing means are even quicker and simplerthan current ones yet are reliable and have low-production costs.

In accordance with the invention, there is provided an implant assembly,comprising: an intrabony implant which is designed to be inserted in afixed manner in the jawbone and is provided with a cavity; an artificialtooth assembly with a tooth stump for the respective artificial tooth,said tooth stump having a lower stem to be inserted and fixed in saidcavity of said intrabony implant, and a said tooth stump having an upperprotrusion for engagement with an artificial tooth; which ischaracterized in that said cavity of said intrabony implant has anundercut annular recess below and above which there are hole portionshaving a smaller diameter, one of said hole portions, above said recess,being interrupted by at least one longitudinal access slot for thepassage of at least one lug of the stem of said tooth stump by axialsliding and subsequent rotation of said stem in said recess, the outerupper end of said intrabony implant being polygonal, said tooth stumpprotruding above said lug with said protrusion having a polygonal regionfor the insertion of a polygonal annular bush for the mutual locking ofsaid stump with respect to said intrabony implant so as to preventrotation.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomeapparent from the detailed description of some embodiments, illustratedonly by way of non-limitative example in the accompanying drawings,wherein:

FIG. 1 is a sectional view of the intrabony metallic implant (generallymade of titanium) according to the invention with a stump associatedtherewith;

FIG. 2 is a plan view of the intrabony implant of FIG. 1;

FIG. 3 is a partially sectional view of the intrabony implant of FIG. 1,taken from the outside;

FIG. 4 is a perspective view of the implant according to the inventionwith a rotation-preventing bush;

FIGS. 5 and 6 are, respectively, a sectional front view and a top viewof an extension ring made of calcinable resin which can be fitted overthe intrabony implant;

FIGS. 7 and 8 are a front view and a top view of a titanium stump;

FIGS. 9 and 10 are an axial sectional front view and a top view of atitanium intrabony implant;

FIG. 11 is a sectional view of the assembly of the components of theintrabony implant in the assembled condition;

FIGS. 12 and 13 are, respectively, a top view and a longitudinalsectional view of an intrabony implant in another embodiment of theinvention;

FIGS. 14, 15 and 16 are, respectively, a top view, a sectional view anda side view of an annular rotation-preventing bush;

FIG. 17 is a side view of a stump;

FIG. 18 is a sectional view of the components in the assembledcondition.

WAYS OF CARRYING OUT THE INVENTION

With reference to the above FIGS. 1 to 11, in a first embodiment theimplant according to the invention comprises a hollow intrabony implant1 to be inserted in a fixed manner in the jawbone, not shown in thefigures, and an artificial tooth assembly which has a stump 3 for therespective artificial tooth, also not shown, with a protrusion 9 forinsertion coupling with said artificial tooth and a lower stem 32 forentering a cavity of the intrabony implant 1 for fixing it.

The cavity of the intrabony implant 1 is composed, sequentially from thetop downwards, of portions 11, 12, 13 and 14 which will be betterdescribed hereinafter.

The cavity is in fact provided with an undercut annular recess 12 andwith at least one longitudinal slot 121 which cooperates with at leastone lug 131 of the stump 3 in order to provide coupling by axialinsertion and subsequent rotation, associated with a beveled lockingcoupling and with an external polygonal shape of both, in order to fit arotation-preventing keying ring 2.

In particular, in the cavity of the intrabony implant 1, below theundercut annular recess 12 there are two hole portions having a smallerdiameter, respectively a conical portion 13 followed by a cylindricalone 14; above said recess there is a hole portion having a smallerdiameter 11 which is interrupted by the longitudinal access slot 121 forthe passage of the lug 131 of the stem 32 of said tooth stump 3.

The outer upper end 192 of the intrabony implant 1 is polygonal.

The tooth stump 3 protrudes beyond lug 131 with two portions 34 and 35which correspond to the portions 13 and 14 of the cavity with which theymate.

The stump 3 is externally provided, above the lug 131, in the part 9that protrudes beyond the intrabony implant 1, when it is inserted, witha polygonal region 193.

The outer shaped regions 192 and 193, of the intrabony implant 1 and ofthe stump 3 respectively, are adapted for the coupling of arotation-preventing locking bush 2 which is shaped internally like apolygonal ring and is suitable to fit around both regions in order to belocked thereat and prevent the mutual rotation of the two parts.

Advantageously, the intrabony outer part of the intrabony implant 1 issanded and consists of two threaded portions 16 and 18 with twodifferent types of thread in order to facilitate insertion and grip.

Both threaded portions 16 and 18 end, in an upward region, withrespective shoulders 161 and 181, each of which is substantially formedby a fishbone wedge so as to improve grip.

Equally advantageously, in the threaded regions there are longitudinalnotches 162 and 182 so as to provide correspond cutting edges for theself-tapping of the intrabony implant 1 on the bone during screwing.

It should also be noted that the mating between the portions 13 of theimplant 1 and 34 of the stump 3, which are beveled, gives greater safetyand solidity to the mating.

With reference now to the above cited FIGS. 12 to 18, in anotherembodiment the implant according to the invention comprises a hollowintrabony implant 201, to be inserted in a fixed manner in the jawbone,not shown in the figures, and an artificial tooth assembly, which has astump 203 for the respective artificial tooth, also not shown, with aprotrusion 209 for engagement with the artificial tooth and a lower stem232 for entering the cavity 210 of the intrabony implant 201 in order tofix it.

The cavity 210 of the intrabony implant 201 is composed, from the topdownwards, of portions 211, 212 and 216 described in detail hereinafter.

The cavity 210 has an undercut annular recess 212 and three longitudinalslots 221 (arranged at 120° to each other), which cooperate with atleast one lug 331 of the stump 203, in order to provide coupling byaxial insertion and subsequent rotation, associated with a mating byvirtue of the external polygonal shape of both parts in order to fit arotation-preventing keying ring 202.

The cavity 210 of the intrabony implant 201 has an undercut annularrecess 212 below which there is a portion 216 of a cylindrical holewhich has a smaller diameter and above which there is a hole portionhaving a smaller diameter 211 which is interrupted by the longitudinalaccess slot 221 for the passage of a lug 331 of the stem 232 of thetooth stump 203 by axial sliding and subsequent rotation.

The lower part 234 of the stump 203 to be inserted in the cavity 210 hasan end part 235 which has a smaller diameter and is covered by acapshaped element 236 made of elastic material (for example Teflon).

The distance between the upper part of the recess 212 and the bottom ofthe cavity 210 is slightly shorter than the distance between the upperpart of the lug 331 and the end of the element 236, so that the latteris slightly compressed upon mating.

Once mating has been provided, the lug 331 is pushed against the upperpart of the recess 212 so as to provide rotation-preventing friction.

The outer upper end 392 of the intrabony implant 201 is polygonal.

The tooth stump 203 protrudes beyond the lug 331 with the part 234 thatcorresponds to the portion 216 of the cavity 210 with which it mates byvirtue of the interposition of the element 236.

The stump 203 is externally provided, above lug 331, in the part 209that protrudes beyond the intrabony implant 201, when inserted, with apolygonal region 393.

The outer shaped regions 392 and 393 of the intrabony implant 201 and ofthe stump 203, respectively, are adapted for the coupling of arotation-preventing annular locking bush 202 which is internallypolygonal and is adapted to fit over both regions so as to be lockedthereat and prevent the mutual rotation of the two parts.

The bush 202 is in fact provided, in an upward region, with notches 337which allow the flexing of a corresponding part thereof which isinternally provided with an annular protruding edge 338 which is adaptedto fit with a snap action in a corresponding annular slot 339 of thestump 203.

Advantageously, the intrabony external part of the intrabony implant 201is formed by two threaded portions 214 and 218 in order to allow easyinsertion and grip.

Both threaded portions 214 and 218 end, in an upward region, withrespective shoulders 361 and 381, each of which substantially forms afishbone wedge so as to improve grip.

Equally advantageously, in the threaded regions there are longitudinalnotches, not shown in the figures, so as to provide correspondingcutting edges for the self-tapping of the implant 1 on the bone duringscrewing.

In practice it has been observed that the intended aim of the inventionhas been achieved, a quick coupling of the bayonet type with axial androtary motion having been achieved which provides the advantage ofadequate safety against loosening and breakage in addition to quickaction.

The invention thus conceived is susceptible of numerous modificationsand variations, all of which are within the scope of the inventiveconcept.

All the details may furthermore be replaced with other technicallyequivalent elements.

In practice, the materials used, as well as the dimensions, may be anyaccording to requirements.

The disclosures in Italian Patent Application No. UD99A000056 from whichthis application claims priority are incorporated herein by reference.

What is claimed is:
 1. An implant assembly, comprising: an intrabonyimplant which is designed to be inserted in a fixed manner in thejawbone and is provided with a cavity; an artificial tooth assembly witha tooth stump for the respective artificial tooth, said tooth stumphaving a lower stem to be inserted and fixed in said cavity of saidintrabony implant, and said tooth stump having an upper protrusion forengagement with an artificial tooth; wherein said cavity of saidintrabony implant has an undercut annular recess below and above whichthere are hole portions having a smaller diameter, one of said holeportions, above said recess, being interrupted by at least onelongitudinal access slot for the passage of at least one lug of the stemof said tooth stump by axial sliding and subsequent rotation of saidstem in said recess, the outer upper end of said intrabony implant beingpolygonal, said tooth stump protruding above said lug with saidprotrusion having a polygonal region for the insertion of a polygonalannular bush for the mutual locking of said stump with respect to saidintrabony implant so as to prevent rotation.
 2. The implant assemblyaccording to claim 1, wherein the external part of the intrabony implantis threaded.
 3. The implant assembly according to claim 2, wherein saidintrabony implant is formed by two conical threaded portions which end,in an upward region, with respective shoulders, each of whichsubstantially forms a fishbone wedge.
 4. The implant assembly accordingto claim 3, wherein in said threaded portions there are longitudinalnotches so as to form corresponding cutting edges for the self-tappingof the intrabony implant on the bone during screwing.
 5. The implantassembly according to claim 1, wherein the mating between the lower stemof said stump and the corresponding cavity is provided by virtue ofcomplementarily shaped conical parts.
 6. The implant assembly accordingto claim 5, wherein the lower stem of said stump to be inserted in saidcavity has an end portion which has a smaller diameter and is covered bya cap-like element made of elastic material, the distance between theupper wall of said undercut recess and the bottom of said cavity beingshorter than the distance between the upper part of said lug and the endof the cap-like element, so that the latter is compressed upon mating.7. The implant assembly according to claim 1, wherein said bush isprovided, in an upward region, with notches which allow the flexing of acorresponding part thereof which is internally provided with a raisedannular edge which is suitable to fit, with a snap action, in acorresponding annular slot of said stump.